The present disclosure relates to the manufacture of semiconductor devices, such as transistors, semiconductor-implemented resistors, diodes, etc. Such transistors include thin film transistors (TFTs), which are useful in many areas of technology, such as electronic applications, including OLEDs, liquid crystal displays (LCDs), photovoltaic devices, integrated circuits, etc.
Transistors, such as field-effect transistors (FETs) may be fabricated using a variety of architectures depending on the type of substrate technology employed, the complexity of the fabrication process, and the desired function and characteristics of the transistor. In the flat panel display industry, TFTs are used for several purposes, including for use as the discrete transistors for switching each pixel of a liquid crystal display (LCD), or for the discrete transistors used to drive the respective pixels of an organic light-emitting diode (OLED) display. There are, of course, many other uses of TFTs in display technologies, including the circuitry related to the discrete pixel circuitry, such as the array control circuitry, driving circuitry, and test circuitry, much of which may be disposed at the periphery of the pixel display area.
FETs may be formed from inorganic material and/or organic materials. Conventional organic transistors are typically formed horizontally on firm or flexible substrates. The transistor structure includes gate, drain and source electrodes, as well as an organic semiconducting layer and an electrical insulating layer (a gate dielectric). The organic semiconducting layer functions as a hole, electron, or ambipolar charge transporting channel. The electrodes are deposited by thermal processes, e-beam evaporation, or sputtering, and usually employ metals, metal compounds, transparent conducting oxides or conducting organic materials.
It is desirable to improve the electrical characteristics of FETs in terms of two important factors affecting transistor performance: (a) the channel field effect mobility of the semiconducting layer, and (b) the charge injection efficiency of carriers from the drain-source electrodes to the channel.